Sewing machines



I J1me 1966 J. c. CHEZAUD ETAL 3,256,844

SEWING MACHINES Filed June 6, 1963 5 Sheets-Sheet l gall Q Inventors June 21, 1966 J. c. CHEZAUD ETAL 3,256,844

SEWING MACHINES Filed June 6, 1963 5 Sheets-Sheet 2 In enlo w tlorney June 21, 1966 J. c. CHEZAUD ETAL 3,256,844

SEWING MACHINES Filed June 6, 1963 5 Sheets-Sheet 3 a 1m 2 3 MI gm i? 3E 3E Attorney United States Patent 00,219 1 Claim. (Cl. 112-207) The present invention relates to sewing machines.

It is known that one of the difiiculties encountered when sewing fabrics made of synthetic fibres is the puckering of the fabric along the sewing line constituted by the stitches executed by the machine.

One of the causes of this puckering is the ease with which the various'layers of fabric can slide on one another. It is an object of the present invention to provide an improved machine which reduces or overcomes this difficulty of puckering.

According to the present invention there is provided an advancing mechanism for a sewing machine, such mechanism having upper and lower feed means driven synchronously to close and grip and advance fabric to be sewn, each feed means having two dogs, the downstream dogs being adapted to feed at a higher rate than the upstream dog whereby the fabric is tensioned.

Lower and upper feed dogs can have serrations or a fiat surface.

The invention also provides a sewing machine including the above advancing mechanism.

According to another aspect of the invention there is provided a method of advancing fabric relative to the needle of a sewing machine such method comprising simultaneously gripping the fabric between a first set of upper and lower feed dogs upstream of said needle and a second set of upper and lower feed dogs downstream of said needle, moving said first set of feed dogs in a downstream direction at a given rate and simultaneously moving said second set of feed dogs in a downstream direction at a higher rate to advance and tension said fabric.

In order that the invention may more readily be tinderstood, the following description is given by way of example reference being made to the accompanying drawings.

In the drawings:

FIGURE 1 shows diagrammatically one embodiment of the present invention, the various parts being shown in the demounted state; 1

FIGURES 2a to 2d show diagrammatically the operation of the device according to the invention; and

FIGURE 3 is a schematic diagram of the control mechanism for closing the embodiment illustrated in URE 1.

In FIGURE 1, a sewing plate 1 ha a hole 2 for the passage of the needle (not shown) along the axis xy, and also has apertures in which are mounted the upstream dog 3 and the downstream dog 4 of the lower feed means. A presser foot 5 ha a relatively small surface area so that it does not press on the lower feed dogs. An upper feed means comprises two parts or upper dogs 6 and 7 which are respectively opposite the upstream dog 3 and the downstream dog 4 of the lower feed means. These two dogs can be given a differential advancing movement by means of a mechanism (not shown) which may be the same type used in conventional sewing machines to which there are also connected the two upper dogs, each of these two upper dogs 6 and 7 being given an advancing movement synchronised with that of the corresponding lower dog. The control mechanism is illustrated schematically in FIGURE 3 and will be described below.

FIG-

The way in which the two feed means operate is shown diagrammatically in FIGURES 2a to 2d.

In FIGURE 2a, the two lower dogs 3 and 4 are at their point of maximum withdrawal relatively to the direction of advance of the fabric (indicated by the arrow the two upper dogs 6 and 7 being similarly positioned. The lower dogs 3 and 4 are retracted below the sewing plate 1 whilst the upper dogs 6 and 7 are situated at a certain distance above the needle plate 1, as is also the needle 8. The two fabrics 9 and 9' which are to be joined together are held in place by the presser foot 5.

In FIGURE 2b, the lower dogs 3 and 4 emerge from.

the sewing plate and hold the fabrics in co-operation with the upper dogs 6 and 7 which are lowered, whilst the presser foot is raised and the needle commences its descending movement.

In FIGURE 2c, the lower dogs 3 and 4 and the upper dogs 6 and 7 have carried out their advancing movement. The two downstream dogs 4 and 7 have advanced by an equal distance greater than the advance of the two upstream dogs 3 and 6; the needle then perforates the fabric.

In FIGURE 2d, the upper dogs 6 and 7 have been raised and the lower dogs 3 and 4 have been retracted whilst the presser foot has descended to hold the fabrics. The needle begins its upward return movement.

The upper and lower dogs then carry out a withdrawing movement and are once more in the position shown in FIGURE 2a, and a new cycle re-commences.

The differential advancing movement, given to the upper and lower feed dogs can, for example, be of the type which is shown schematically in FIGURE 3. The drive shaft 10 transmits a reciprocating movement to the needle bar 12 through a crank and connecting-rod system 11. A movement synchronised with that of the needle 8 is transmitted to the hook shaft 16 by means of direction changes such as bevel gears 13 and 14 and shaft 15. Two eccentrics 17 and 18 fixed to the drive shaft 10, transmit to'the upstream and downstream feed dogs 3 and 4 both an advancing and retracting and a raising and lowering movement. The advance and retracting displacement given to the downstream feed dogs 4 is greater than that given to the upstream feed dogs 3 because of the lever 30 the position of which determines the displacement of dogs 3. One could equally well control the movement of the lower feed dogs '3 and 4 through eccentrics fixed to shaft 16. p

By means of the bevel gears 19, 20, 21, 22 and shafts 23, 24 and 25 a movement is given to shaft 26 synchronised with the movement of shaft 16. Two further eccentrics '27 and 28 are mounted on shaft 26 to transmit to the upper feed dogs 6 and 7 and advancing and retarding movement. Another eccentric 29 provides a raising and lowering movement of the upper feed dogs relatively to the presser foot, the shaft 25 being formed telescopically to permit displacement of the presser foot 5.

The eccentrics 27 and 28 are arranged to advance the upper dog 6 by an amount equal to the advance of the lower dog 3 and to advance the upper dog 7 by an amount equal to the lower dog 4.

The eccentric 29 causes alternating of the movement of the presser foot and the upper feed dogs 6 and 7, so that, as the fabric is clamped by the presser foot 5, the fabric acts as a reaction member for the presser foot, so that the feeddogs will rise. Similarly, when the eccentric 29 rotates the feed dogs 6 and 7 grip and react against the fabric, to 'cause raising of the presser foot.

We claim:

In a sewing machine having a needle, a feed mechanism for feeding fabric'to said needle, such mechanism comprising a first set of upper and lower feed dogs upstream of said needle; a second set of upper and lower feed dogs downstream of said needle; means for moving the dogs of each said set from an open position to a closed position synchronously, eifective to grip fabrics to be sewn, said means including a vertically displaceable rotatable horizontal drive shaft, an eccentric mounted on said shaft for rotation therewith and operatively connected to the upper dogs of each of said first and second sets, for raising and lowering of said upper dogs; presser foot means between said first and second sets; said presser foot means being operatively associated with said shaft to grip fabrics to be sewn when said feed dogs are in said open position, said presser foot being vertically displaceable with said shaft, whereby when said shaft rotates said eccentric to cause said upper feed dogs to move downwardly to contact the fabric to be fed, said contact will cause said shaft to move upwardly thus raising said presser foot by reaction; and means for advancing said first set of feed dogs in a direction towards said needle at a given rate; and means for advancing said second set of feed dogs in said direction at a higher rate.

References Cited by the Examiner FRANK J. COHEN, Primary Examiner.

JORDAN FRANKLIN, R. J. SCANLAN, JR.,

. Assistant Examiners. 

